Time Fuses

Pyrotechnics have been used for military purposes for many centuries as propellants, explosive charges, time fuses, and for illumination. There are still many uses of pyrotechnic devices in military appHcations, where they provide portability, storage stability, simplicity of operation, safety, and the reUability required for military scenarios. The devices must be capable of surviving rough handling, weather extremes, and extended storage, yet reUably perform when called on to function. 

Zeit-raum, m. time interval, period, -rech-nung, /. chronology. -schnur, /. time fuse. 

Zeit-wort, n. verb. -2Under, m. time fuse delay-action cap, delay igniter. -2iindung, /. delayed ignition. -2wischenrauni, m. time interval. 

FIG. 10 SEM micrographs of (a) sUica nanoparticle/polymer [Si02/PDADMAC)3]-coated PS lat-ices and (b) hollow silica capsules. The hollow sUica capsules were obtained by calcining coated particles as shown in (a). The calcination process removes the PS core and the polymer bridging the silica nanoparticles, while at the same time fusing the silica nanoparticles together. Some of the silica capsules were deliberately broken to demonstrate that they were hollow (b). (From Ref. 106.)... 

Time fuse, or safety fuse, which is used in most nonelectric firing systems, is available in a multitude of varieties, both in color and rate of burning. 

By all odds, the most frequent cause of misfires in nonelectric systems is failure to seat the blasting cap firmly on the time fuse. Here s the proper way to do it ... 

Primacord, or detonating cord, differs from time fuse in that it detonates practically instantaneously along its entire length rather than burning progressively and relatively slowly. 

Depending upon the purpose and circumstances of the job to be done, the operator will need different ways of setting off his charges. He may need only a short delay, such as may be provided by a piece of time fuse, to permit him to get out of range of the explosion. He may need a reasonably accurate delay of several hours. He may wish to initiate the action instantaneously himself at a precise moment. Or he may wish to have the action initiated by the target. 

Inspection will reveal a shallow depression in the open end of the detonator. This depression, about y inch deep, is sufficient to permit the crimping of the detonator to time fuse if care is taken. See Figure 22. In lieu of crimping, the detonator can be taped to the fuse. 

MATERIALS Tin can or bottle, sand, stones, strong cord, TNT or plastic explosive, nonelectric blasting cap, delay firing device (time pencil or time fuse). 

Although more powerful than military fragmentation grenades, the improvised version described below is not as easily armed and thrown. It is advisable, therefore, to thoroughly test the time fuse used and perhaps to practice with a dummy model of the grenade before attempting to use a live one operationally. 

MATERIALS Metal fragments (nails, washers, bolts, nuts, screws, etc.), rags, string or tape, time fuse, nonelectric blasting cap, % pound of any high explosive. 

Prepare a time fuse fire starter as described and illustrated in the following section on improvised incendiaries. See Figure 59. Insert the fire starter among the match heads and wedge it se-... 

The rocket can now be fired from an improvised launcher by lighting the time fuse. 

ALTERNATIVES A spoonful of match head igniter (match head scrapings) can be used in place of the 20 match heads. A magnesium head time pencil, or a time pencil to which is attached a small sack or paper tube loosely filled with black powder, can be substituted for the match heads and the time fuse fire starter. 

Chlorate-sugar is easily ignited by the flame of a match, the spit of a percussion cap or time fuse, the heat of an incandescent wire, or upon contact with concentrated sulfuric acid. 

To use, place several spoonfuls of the mixture on the material to be lit and add a spoonful of chlorate-sugar on top. Be sure the safety (time) fuse or other spark-producing delay system is placed so it will act upon the chlorate-sugar mixture first. 

Ignition can be by time fuse, firecracker fuse, a spark, or concentrated sulfuric acid. 

Several igniters or first fire mixes can be set off by a spark from time fuse. Others require a stronger flame. Time fuse, plus matches, can be combined to provide this more intense initial flame. 

About 14 inch from the end of a piece of time fuse cut a notch with a sharp knife so that the powder train is exposed. 

An easy, effective way to use this mixture is to put about a quart of it in a paper bag and place the bag on the target material. The bag can be lit with a match and the mixture will ignite quite readily. It bums as well as napalm. If a longer delay time is required, use one of the igniter mixes described earlier along with time fuse or other delay device. The time fuse alone, however, will not ignite the incendiary mix. 

A1 + KCIO3) and in back of the latter a time fuse. The operator hid in a hole and, at the approach of the tank, ignited the fuse" which, in turn, ignited the thermite. Just as soon as the heat of the thermite melted the resin, the device was-struck (by the operator) to the bottom armor plate of the tank. At the same time the heat of the thermite set off the detonator and this in turn initiated the main charge This device was in an experimental stage when the war terminated Ref 1) E.E. Richardson et al, CIOS Rept 25-18 (1945), pp 23-5 2) PATR 2510 (1958), p Ger 87-L R... 

A more complicated tracer-incendiary shell was used by the British and Germans. In this shell (usually 75mm), the flash from the time fuse was transmitted through a tube (located in the center of the cylinder and extending from the top, near the fuse, almost to the bottom of the shell) to the primer. The primer ignited the incendiary composition, containing Mg, Ba(N03 )2, and binder with or without Sr(N03)2, and blew out the base of the shell. This resulted in emission of flame from the base of the shell, lasting about 15 seconds... 

The Stoke s bombs were loaded for best results with about 7.5 lbs of thermite as the incendiary compound, and ophorite as the explosive igniter. The ignition was started by a time fuse... 

Two types of fuse are in common use by the US Army (1) blasting time fuse that has a spiral wrapped outer cover usually colored orange and (2) safety fuse M700 that has a smooth green plastic cover with Length markers of abrasive material (so they can be felt in the dark). These two types of fuse are shown in Fig 2 (Ref 1)... 

D. A. Davies [7] suggested the use of explosive charges for rain-making. The charges, consisting of 15 g of blackpowder plus 1.5% of silver iodide, are sent by balloon into a cloud, where they are exploded by a time fuse. The particles of silver iodide thus released act as nuclei on which the water vapour in a raincloud coagulates, to fall as rain drops. 

The LE s change from a solid to a gaseous state relatively slow (in a matter of milliseconds, 10 secs). They deflagrate progressively over a relatively sustained period of time, and this action can be utilized to push, heave or shove, rather than to rend or tear, the object against which they are placed. The principal military uses of deflagrating expls are as proplnt chges for projectiles and as the powder train in a time fuse. The... 

A fuzing application for Ca silicide is discussed in a current Brit patent (Ref 18) which claims mechanically insensitive and thermally stable timing fuses with burning rates of 100—500 sec/m (with a variation of 52%) can be manufd with a pyrot type powder core consisting of 20—67.3% K nitrate, with the remainder Ca silicide. The silicide is also used as a fuel in priming compns. Meyer (Ref 1) suggested that it be used to the extent of 15% with MF (25%),... 

Torpedo. A marine weapon consisting of an underwater vehicle, a warhead, and a control mechanism, which can be a homing unit, an impact or proximity device or a time fuse. Initially developed as a surface-to-surface weapon, the torpedo has evolved into a diversified class of weapons capable of submerged launching or targeting — or both... 

Potassium nitrate (together with sulfur and charcoal) is used in the manufacture of gunpowder (black powder). When such a mixture is ignited by means of a spark, both gaseous and solid decomposition products are produced in the resulting explosive reaction, which is quite complex. Black powder is used in the manufacture of ammunition for small firearms, in the production of time fuses, and as a blasting powder in mining operations. 

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